v1.12.0 - 50 checks

Eleven new checks, reaching 50 total: CH040-CH050. Mostly flake8-bugbear/pyflakes ports (B003/B015/B016/B017/B018/B022/B023/B025/B029/B035, F631) plus one original idea, CH047 (@contextmanager cleanup skipped when the with-block body raises) - real hits found in litellm, peft, agno, and mlflow.

Three checks were built, corpus-scanned, and rejected outright before this batch shipped (an assignment-from-.sort() check that collided with NumPy/PyMongo/HuggingFace Dataset/custom .sort() methods; an enum-duplicate-value check where every real hit was a deliberate "rolling alias" pattern; an eq-without-hash check where every real hit was an intentional, documented value-object design). Full reasoning in docs/FINDINGS.md.

CH049 and CH050 each needed a real precision fix after their first corpus scan - see docs/FINDINGS.md for the before/after counts.